The way the D18 worked allowed for the OD unit. To do that with the D300, you'd need a 5spd trans.

 

How hard is it to convert to the 5 speed?

Is the strength and reliability with really low gearing the same as the Tremec 4 speed?


My truck has 456 gears with lockers and the 4.25.1 low gear kit in the Dana 300 with 33" tires.
I am still waiting for the Delivery of the Truck its still in TN right now will probably be another week or so before I see it for first time.
I am super excited to finaly have another CJ

 

4.56 gears are really low for any tire under 35". Unless your plans include larger tires you may want to think about regearing.

 

I may have to go with a Bigger lift kit and bigger tires then? What do you guys suggest? Its got a 4 inch now how much tire can I get under it with a 4 without rubbing issues and still have good articulation without hitting? I am in Southern Nevada and plan on doing some serious off road work outs including lots of rocks.... Cant help it i am into Metal detecting lol

I will be contacting GEAR VENDORS tomorrow about a real over drive unit that bolts to the output of transfer case and is locked out when in 4 wheel drive but they are not cheap 3-4K range. I can do a lot of lifting and new rims and tires for that much.

I guess this thing had been set up for extreme rock crawling is all I can figure? the previous owner said they used to haul it to places to go trail riding? what kinda trails are in TN is all I wonder lol. I traveled all over Alaska back in the 80s off road and only ever gat stuck Twice! with a stock cj7 with a 304

 

I may have to go with a Bigger lift kit and bigger tires then? What do you guys suggest? Its got a 4 inch now how much tire can I get under it with a 4 without rubbing issues and still have good articulation without hitting? I am in Southern Nevada and plan on doing some serious off road work outs including lots of rocks.... Cant help it i am into Metal detecting lol

I will be contacting GEAR VENDORS tomorrow about a real over drive unit that bolts to the output of transfer case and is locked out when in 4 wheel drive but they are not cheap 3-4K range. I can do a lot of lifting and new rims and tires for that much.

I guess this thing had been set up for extreme rock crawling is all I can figure? the previous owner said they used to haul it to places to go trail riding? what kinda trails are in TN is all I wonder lol. I traveled all over Alaska back in the 80s off road and only ever gat stuck Twice! with a stock cj7 with a 304

I think the GV units are a little overrated. I currently have one in my 1977 Ford Lowboy. It lowers the RPM by about 300rpms (with a C6 auto)...which really isn't worth it. There's also a Ranger Overdrive torque splitter. But you would need to install a compatible 4 speed (such as a NP435) transmission to make it work. I also have one of those in my 1972 Highboy. I don't think any overdrive unit is a good combo in any short wheelbase vehicle (the units are just too darn long). Converting to a 5 speed is really the way to go.

 

double post

 

There are several 5 speed transmissions that will work in you CJ-7 with a Dana 300. I have a NV4500 and really like it. They are not cheap, but you will probably never break one in a lightweight Jeep application. I have 4.56 gears, a Dana 300 and 33" tires.

There are at least 2 companies that make adapter plates to mate a NV4500 to a Jeep engine. Mine is mated to a 5.0 EFI motor out of a Mustang that has been transplanted into my Jeep.

A T5 should be a even trade strength wise for you T4. I think you have to change drive line lengths but it should hold up as well as your T4.

 

I am gonna look at all my options but like the idea of the NV4500 I may be able to find one in a Junk yard?

Stonetower whats your rpm on the hiway?

 

I am gonna look at all my options but like the idea of the NV4500 I may be able to find one in a Junk yard?

At a pick and pull style of junk yard?...Pretty close to a zero chance of ever finding one, but i suppose you might luck out and find one. If you do, just make sure to by a lotto ticket after that since it would be your lucky day. Also, a normal junk yard should have them...but probably at a hefty price though. They will know exactly what it's worth and then mark up the price another 50% to 100%.

 

Around 2400 at 65 MPH.

http://www.novak-adapt.com/knowledge/transmissions/manual/nv4500

https://www.advanceadapters.com/nv4500-transmission.php

When in 2 low when I am hunting, I have been known to drive down the highway a bit to get to the next logging road without shifting out of low range by using 5th gear to drive a about 30 miles per hour. It comes in handy. I would not want put a load on it in 5th gear while in low, but on a smooth highway, to scoot a half mile to the next road works really well.

 

So far it seams that it may be my best option.
I read on a couple web sights it says its even stronger than the 4 speed I have in there now.

I can live with 2400 on the hi way, wondering if 35s will fit on her now? Maybe with a body lift?

 

I think a set of BSD 4 inch springs might be a better choice for a lift.

 

I didnt ask previous owner what brand kit of lift was used. I can call and ask him.

 

The Jeep will be much more drivable with the 33 inch tires and a 5 speed transmission. Unless you need the 35s or want them, it is harder to get in the Jeep, they cost more, and it will be harder to start the Jeep out from a stop with a given gear set and a bigger tire vs a smaller tire. If you are wanting a 5 speed, start with that and then decide if you need or want bigger tires.

 

There's also the NV3500 and AX15 5 speeds. Not as heavy duty as a NV4500 but pretty reliable quite a bit stronger than a T5.

 

When my CJ7 still had the 258, 4:56, and 32” or 33” tires, I had an NV4500 in it. I hated the transmission from day one....now hear me out...
I did have a T5 prior to the NV and I liked the gearing combo quite a bit (for use in the muddy PacNW). When I installed the NV, it changed the whole dang optimum gear ratio that I liked. The low first gear wasn’t usable for most things. I would have liked a little bit taller first gear. The 258 engine didn’t have quite enough torque to pull lots of hill climbs with the NV’s second gear ratio. When I finally swapped in a RamJet 350, then the NV transmission because awesome for me.

In a different CJ build that I’m working on i went with a 4.0 /NV3400 / D300 / Klune-V “David” box. I have high hopes for that drivetrain combo. I’ll probably stick with 35’s on this Jeep.

 

Up date

I rebuilt the front end Dana 50 in my Ford F250 and drove it up to TN with my Tow Dolley last week and picked up the CJ got home a few days ago.
I took the Jeep for a short drive there but not in 4x4 not it till I got it home just wanted to make sure it ran and drove.

So got it home got it unloaded and took it up to gas station as it was empty then headed for local hills by my house.

Truck doesn't drive to bad in my opinion I got it up to 50 mph and I didnt think the RPM was too bad, has a few unexpected rattles I have to figure out but nothing that sounds like its falling apart or anything,


Truck is a Mountain Goat wants to go Tires are some sort of Mud Tire very soft and I dont want to tear them up in the Nevada Rocks so I called it a bit early on, I want to sell these tires to help pay for a set of Rock tires or I may put them on my 69 Dodge Power wagon for time being. I really need to get un attached to all the junk I have.lol


Plan to fix this one up a Bit and hit the trails do some Gold hunting and Troat fishing in hard to get too places with it. Maybe do a Jeep club thing or two with as well.

I also just picked up a 07 Commander yesterday looking at putting a Lift on that after I fix the engine in it, it has a Blown head gasket I think blowing white smoke.
I have even more questions about that rig.